Sensory and ATP derivative-based indicators for assessing the freshness of Atlantic salmon (Salmo salar) and cod (Gadus morhua)

peer-reviewedIrish Journal of Agricultural and Food Research | Volume 58: Issue 1 Sensory and ATP derivative-based indicators for assessing the freshness of Atlantic salmon (Salmo salar) and cod (Gadus morhua) Colin Fogarty , Conor Smyth , Paul Whyte , Nigel Brunton and Declan Boltonemail DOI: https://doi.org/10.2478/ijafr-2019-0008 | Published online: 31 Oct 2019 PDF Abstract Article PDF References Recommendations Abstract To estimate the shelf life of fresh fish, the processor must know the period of time between catch/harvest and arrival at the processing plant. This information is not always available, necessitating the provision of methods to estimate the time since catch or harvest. The objectives of this study were therefore to develop and/or validate sensory and ATP derivative-based methods for rapidly assessing the freshness of fish. A quality index method (QIM; raw fish) and a quantitative descriptive analysis (QDA; cooked fish) were developed and validated (against bacterial count [total viable count (TVC)] and time) for salmon (Salmo salar) and cod (Gadus morhua). The production of inosine monophosphate (IMP), inosine and hypoxanthine (Hx) and associated ratios (IMP/Hx, K1-value or H-value) were also investigated for use as freshness markers. There was a linear relationship between QIM and TVC (R2 = 0.93 for salmon and R2 = 0.89 for cod), QIM and time (R2 = 0.96 for salmon and R2 = 0.98 for cod), QDA and TVC (R2 = 0.93 for salmon and R2 = 0.77 for cod) and QDA and time (R2 = 0.94 for salmon and R2 = 0.87 for cod), suggesting that the QIM and QDA schemes developed could be used to monitor/assess freshness. The H-value also increased linearly with TVC (R2 = 0.88 for salmon and R2 = 0.89 for cod) and time (R2 = 0.93 for salmon and R2 = 0.84 for cod). It was therefore concluded that both the QIM/QDA approach and monitoring ATP degradation, specifically expressed as the H-value, could be used as rapid methods to assess the freshness of salmon and cod arriving at the processing plan

Reflex impairment as a measure of vitality and survival potential of Atlantic cod (Gadus morhua)

A ssur ing the v itality and survival potential of live-caught Atlantic cod (Gadus morhua) is important for improving the sorting of fish before net penning operations designed to hold fish for growth and later market. When Atlantic cod are captured by Danish seine, the most commonly used fishing gear for live-caught fish, they undergo stressors such as forced swimming, net abrasion, and air exposure. Laboratory experiments (at an air temperature of 9°C and water temperature of 8°C) were conducted with the aim of constructing a RAMP (reflex action mortality predictor) curve for prediction of vitality and survival potential in Atlantic cod captured in Danish seines, by varying the levels of these stressors. Atlantic cod exposed to increased duration in air (5–20 min) showed increased reflex impairment and mortality, with 75% mortality at 10 minutes of air exposure. Forced swimming in combination with net abrasion and air exposure did not increase reflex impairment or mortality above that associated with air exposure alone. The Atlantic cod RAMP curves indicated that fish with reflex impairment less than 50% would not show mortality and would likely recover from capture stress

Advances in methods for determining fecundity: application of the new methods to some marine fishes

Estimation of individual egg production (realized fecundity) is a key step either to understand the stock and recruit relationship or to carry out fisheries-independent assessment of spawning stock biomass using egg production methods. Many fish are highly fecund and their ovaries may weigh over a kilogram; therefore the work time can be consuming and require large quantities of toxic fixative. Recently it has been shown for Atlantic cod (Gadus morhua) that image analysis can automate fecundity determination using a power equation that links follicles per gram ovary to the mean vitellogenic follicular diameter (the autodiametric method). In this article we demonstrate the precision of the autodiametric method applied to a range of species with different spawning strategies during maturation and spawning. A new method using a solid displacement pipette to remove quantitative fecundity samples (25, 50, 100, and 200 milligram [mg]) is evaluated, as are the underlying assumptions to effectively fix and subsample the ovary. Finally, we demonstrate the interpretation of dispersed formaldehyde-fixed ovarian samples (whole mounts) to assess the presence of atretic and postovulatory follicles to replace labor intensive histology. These results can be used to estimate down regulation (production of atretic follicles) of fecundity during maturation

Hemoglobin genotype has minimal influence on the physiological response of juvenile atlantic cod (Gadus morhua) to environmental challenges

Hemoglobin (Hb) polymorphism in cod is associated with temperature‐related differences in biogeographical distribution, and several authors have suggested that functional characteristics of the various hemoglobin isoforms (HbIs) directly influence phenotypic traits such as growth rate. However, no study has directly examined whether Hb genotype translates into physiological differences at the whole animal level. Thus, we generated a family of juvenile Atlantic cod consisting of all three main Hb genotypes (HbI‐1/1, HbI‐2/2, and HbI‐1/2) by crossing a single pair of heterozygous parents, and we compared their metabolic and cortisol responses to an acute thermal challenge (10&deg;C to their critical thermal maximum [CTM] or 22&deg;C, respectively) and tolerance of graded hypoxia. There were no differences in routine metabolism (at 10&deg;C), maximum metabolic rate, metabolic scope, CTM (overall mean 22.9&deg; &plusmn; 0.2&deg;C), or resting and poststress plasma cortisol levels among Hb genotypes. Further, although the HbI‐1/1 fish grew more (by 15%&ndash;30% during the first 9 mo) when reared at 10&deg; &plusmn; 1&deg;C and had a slightly enhanced hypoxia tolerance at 10&deg;C (e.g., the critical O2 levels for HbI‐1/1, HbI‐2/2, and HbI‐1/2 cod were 35.56% &plusmn; 1.24%, and 40.20% &plusmn; 1.99% air saturation, respectively), these results are contradictory to expectations based on HbI functional properties. Thus, our findings (1) do not support previous assumptions that growth rate differences among cod Hb genotypes result from a more efficient use of the oxygen supply&mdash;that is, reduced standard metabolic rates and/or increased metabolic capacity&mdash;and (2) suggest that in juvenile cod, there is no selective advantage to having a particular Hb genotype with regards to the capacity to withstand ecologically relevant environmental challenges.<br /

Comparative Growth and Survival of Juvenile Atlantic Cod (Gadus morhua)Cultured in Copper and Nylon Net Pens

Bio-fouling on net pens has been a major concern for the marine aquaculture industry. As cage systems increase in size, so does the surface area for the attachment of colonial organisms that create drag on the net, reduce water flow important to fish health, and increase operational expenses due to net cleaning. To solve this problem, the International Copper Association (ICA) has been developing copper alloy netting for sea cages. Copper netting has unique properties that minimize bio-fouling, reduce the risk of fish escapement, prevent predators from entering the net pen, and is recyclable. To test the alloy netting, an experiment was conducted to compare juvenile cod cultured in traditional nylon nets with cod grown in Seawire copper netting ([email protected]). Six, 0.78 m3 cages were each stocked with 200 Atlantic cod (Gadus morhua) averaging 29 ± 2.2 g and grown for 4 months in coastal waters of New Hampshire, USA. Results of the study indicated no significant differences in cod growth, survival, feed conversion ratio (FCR), specific growth rate (SGR), or Fulton’s condition factor (K) between the fish grown in the copper alloy and nylon nets. A chemical analysis was conducted on the cod and indicated no differences in copper levels in muscle, liver and gill tissues taken from the net treatments. Nylon nets with antifouling paint accumulated significantly more bio-fouling than the copper nets. Materials that were in direct contact with the copper netting (plastic cable ties) fouled heavily with hydroids indicating minimal leaching to the environment. This study describes some of the beneficial attributes of copper netting, however future studies need to be conducted over a longer period of time, on a larger scale, and in a more energetic environment to definitively test the utility of this new product

A decade of monitoring Atlantic cod Gadus morhua spawning aggregations in Massachusetts Bay using passive acoustics

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Caiger, P. E., Dean, M. J., DeAngelis, A. I., Hatch, L. T., Rice, A. N., Stanley, J. A., Tholke, C., Zemeckis, D. R., & Van Parijs, S. M. A decade of monitoring Atlantic cod Gadus morhua spawning aggregations in Massachusetts Bay using passive acoustics. Marine Ecology Progress Series, 635, (2020): 89-103, doi:10.3354/meps13219.Atlantic cod Gadus morhua populations in the northeast USA have failed to recover since major declines in the 1970s and 1990s. To rebuild these stocks, managers need reliable information on spawning dynamics in order to design and implement control measures; discovering cost-effective and non-invasive monitoring techniques is also favorable. Atlantic cod form dense, site-fidelic spawning aggregations during which they vocalize, permitting acoustic detection of their presence at such times. The objective of this study was to detect spawning activity of Atlantic cod using multiple fixed-station passive acoustic recorders to sample across Massachusetts Bay during the winter spawning period. A generalized linear modeling approach was used to investigate spatio-temporal trends of cod vocalizing over 10 consecutive winter spawning seasons (2007-2016), the longest such timeline of any passive acoustic monitoring of a fish species. The vocal activity of Atlantic cod was associated with diel, lunar, and seasonal cycles, with a higher probability of occurrence at night, during the full moon, and near the end of November. Following 2009 and 2010, there was a general decline in acoustic activity. Furthermore, the northwest corner of Stellwagen Bank was identified as an important spawning location. This project demonstrated the utility of passive acoustic monitoring in determining the presence of an acoustically active fish species, and provides valuable data for informing the management of this commercially, culturally, and ecologically important species.Thanks to Eli Bonnell, Genevieve Davis, Julianne Bonell, Samara Haver, and Eric Matzen for assistance in MARU deployments, Dana Gerlach and Heather Heenehan for help in passive acoustic data analysis, and the NEFSC passive acoustics group for useful discussions. Funding for 2007−2012 passive acoustic surveys was provided by Excelerate Energy and Neptune LNG to Cornell University. Fieldwork for 2013−2015 was funded through the 2013−2014 NOAA Saltonstall-Kennedy grant program (Award No. NA14NMF4270027), and jointly funded by The Nature Conservancy, Massachusetts Division of Marine Fisheries, and the Cabot Family Charitable Foundation. Funding for 2016 SoundTrap data was provided by NOAA’s Ocean Acoustics Program (4 Sanctuaries Project)

Infection levels and species diversity of ascaridoid nematodes in Atlantic cod, Gadus morhua, are correlated with geographic area and fish size

Atlantic cod (Gadus morhua) is among the most important commercial fish species on the world market. Its infection by ascaridoid nematodes has long been known, Pseudoterranova even being named cod worm. In the present study, 755 individuals were sampled in the Barents, Baltic and North Seas during 2012–2014. Prevalences for Anisakis in whole fish and in fillets in the different fishing areas varied from 16 to 100% and from 12 to 90% respectively. Abundance was also greatly influenced by the sampling area. Generalized additive model results indicate higher numbers of Anisakis in the North Sea, even after the larger body size was accounted for. Numbers and prevalence of Anisakis were positively related to fish length or weight. The prevalence of parasites in whole fish and in fillets was also influenced by the season, with the spring displaying a peak for the prevalence in whole fish and, at the same time, a drop for the prevalence in fillets. Whereas 46% of cod had Anisakis larvae in their fillets, the majority (39%) had parasites mainly in the ventral part of the fillet and only 12% had parasites in their dorsal part. This observation is of importance for the processing of the fish. Indeed, the trimming of the ventral part of the cod fillet would allow the almost total elimination of ascaridoids except for cod from the Baltic Sea where there was no difference between the dorsal and the ventral part. The presence of other ascaridoid genera was also noticeable in some areas. For Pseudoterranova, the highest prevalence (45%) in whole fish was observed in the Northern North Sea, whereas the other areas had prevalences between 3 and 16%. Contracaecum was present in every commercial size cod sampled in the Baltic Sea with an intensity of up to 96 worms but no Contracaecum was isolated from the Central North Sea. Non-zoonotic Hysterothylacium was absent from the Baltic Sea but with a prevalence of 83% in the Barents and the Northern North Sea. A subsample of worms was identified with genetic-molecular tools and assigned to the species A. simplex (s.s.), A. pegreffii, P. decipiens (s.s.), P. krabbei, C. osculatum and H. aduncum. In addition to high prevalence and abundance values, the cod sampled in this study presented a diversity of ascaridoid nematodes with a majority of fish displaying a co-infection. Out of 295 whole infected fish, 269 were co-infected by at least 2 genera

Implications of fisheries during the spawning season for the sustainable management and recovery of depleted fish stocks: a conceptual framework

Fishing during the spawning season may negatively affects the reproductive potential and reproductive dynamics of exploited fish stocks due to a variety of mechanisms such as the disturbance of the natural spawning behaviour, effects on the age, size and sex composition of the spawning population and effects on the population genetics. The effect may differ between species in relation to the spawning strategy and population dynamic characteristics. Based on first principles of reproductive biology, population biology and fishing methods, a theoretical framework is developed on the effects of fishing during the spawning period. This framework is used to structure a review of the available scientific evidence. Implications of the findings on the recovery of depleted fish stocks and the sustainability of exploitation will be discussed and illustrated for a selection of North Sea fish stocks (flatfish, roundfish and pelagic)

Effects of fishing during the spawning period: implications for management

Avoidance of fishing during the spawning season has been proposed as a contribution to achieving sustainable exploitation. Here we review the biological effects of fishing during the spawning period and explore their implication on sustainable management. A distinction will be made between direct mortality and indirect effects. The latter will review how fishery disturbance will affect the physiology and behaviour. Based on the results, a classification scheme is presented of the vulnerability for fisheries during the spawning period. Finally the implications for the population dynamics and fisheries management are discussed